Re: dirty fenders
Regular paint will just crack and peel right off those vinyl fenders.
However, go visit your local auto parts store and look for vinyl upholstery paint. It's available in many colors, and actually bonds perfectly with vinyl. You'll have to go darker than the current fender color, but if you follow the instructions and apply it correctly, it should do just fine.
SEM is a good brand. Rustoleum also makes vinyl pait.